THE death of well-known dolphin Gizmo is an indication that “all is not well” with the Swan River, says historian and environmentalist Dr Sue Graham-Taylor.
Six-year old Gizmo made headlines in 2012 after Water Police successfully freed the calf from the fishing line he had been tangled in for almost two months.
Dr Graham-Taylor said Gizmo’s death last month and the deaths of other river dolphins in the past few years showed that the river was under stress.
“The pressures on the river are both man-made and natural,” Dr Graham-Taylor the Nedlands resident said.
Pathologists at Murdoch University are still investigating the cause of Gizmo’s death but preliminary findings suggest he was suffering from septicaemia caused by a long-term infection.
Gizmo’s gastrointestinal tract was empty, indicating he had not fed recently.
A Department of Parks and Wildlife spokeswoman said there were signs that the condition of the river was improving.
Dr Graham-Taylor said Perth’s river dolphins had become an icon of the Swan River but the death of Gizmo last month revealed the waterway was under stress.
“Human use in the sub-catchments of the Swan-Avon River system increases nutrients, especially phosphorus and nitrogen – that by run-off, through many drains or through groundwater enter the river,” she said.
“We have also lost the river’s fringing vegetation as we have reclaimed, straightened and walled the river.
“We have created grassed areas for recreation but lost the vegetation so vital for reducing nutrients and sediments entering the waterway, stabilising riverbanks and supporting a variety of bird species and other small animals.”
Dr Graham-Taylor said it was important to understand the river’s history in order to help protect it.
“An understanding of its history and an awareness of the state of the River can help us act to preserve and restore this heritage icon for future generations,” she said.
A Department of Parks and Wildlife spokeswoman said that in 2009, six dolphins died in the space of three months but there were signs that the condition of the river was improving.
“Subsequent testing revealed that a natural Morbillivirus was a key factor underpinning those deaths,” she said.
“Morbillivirus affects dolphins and other marine mammals in waterways and oceans around the world and was not related to the health of the Swan River.
“Monitoring undertaken with Murdoch University in recent years has indicated that fish communities are in good to fair shape and there has been an overall improvement in estuarine condition since the mid- 2000s.”
Dr Graham-Taylor will present a talk on the Swan River’s history on November 25, as part of Heritage Perth’s Walk and Talk series.